feat(euvd): link every CVE to its ENISA EUVD record

The EUVD link on the detail page only appeared when enrichment had
stored an euvd_id, which only happens for rows the EUVD KEV feed
covers. Every other CVE showed no EU record at all.

The EUVD resolves a CVE id to the same page as its own EUVD-ID
(/vulnerability/CVE-2026-68820 == /vulnerability/EUVD-2026-56468), so
the link needs no id mapping: use the EUVD-ID when we know it, the CVE
id otherwise. Label keeps the EUVD-ID in parentheses when present.

frontend/app/vulnerabilities/[id]/page.tsx

@@ -757,21 +757,23 @@ export default function VulnerabilityDetailPage() {
                             >
                                 Exploit-DB →
                             </a>
-                            {/* ENISA EUVD — the EU authoritative record. Only
-                                with a known EUVD-ID: the id is not derivable
-                                from the CVE, so without it there is nothing to
-                                link to that would not be a guess. */}
-                            {vuln.euvd_id && (
-                                <a
-                                    href={`https://euvd.enisa.europa.eu/vulnerability/${vuln.euvd_id}`}
-                                    target="_blank"
-                                    rel="noopener noreferrer"
-                                    title={`ENISA EUVD record ${vuln.euvd_id}`}
-                                    className="inline-flex items-center gap-2 px-4 py-2 bg-indigo-50 text-indigo-700 rounded-lg hover:bg-indigo-100 transition-colors font-mono text-sm"
-                                >
-                                    ENISA EUVD ({vuln.euvd_id}) →
-                                </a>
-                            )}
+                            {/* ENISA EUVD — the EU authoritative record. The
+                                EUVD resolves a CVE id to the same page as its
+                                own EUVD-ID, so every CVE gets a link: the
+                                EUVD-ID when enrichment knows it (only KEV rows
+                                do), the CVE id otherwise. No mapping table
+                                needed. */}
+                            <a
+                                href={`https://euvd.enisa.europa.eu/vulnerability/${vuln.euvd_id || vuln.cve_id}`}
+                                target="_blank"
+                                rel="noopener noreferrer"
+                                title={vuln.euvd_id
+                                    ? `ENISA EUVD record ${vuln.euvd_id}`
+                                    : `ENISA EUVD record for ${vuln.cve_id}`}
+                                className="inline-flex items-center gap-2 px-4 py-2 bg-indigo-50 text-indigo-700 rounded-lg hover:bg-indigo-100 transition-colors font-mono text-sm"
+                            >
+                                ENISA EUVD{vuln.euvd_id ? ` (${vuln.euvd_id})` : ''} →
+                            </a>
                             {/* Always offered: the repo advisory search when the
                                 product maps to a repo that publishes its own
                                 (the only place those records exist), otherwise